Just a FWIW here...
I used to use an old Electric Blanket heater in my eye piece box & made another
for the finder scope.
Terminating the "Lizt" (sp?), wire can be a tad iffy but I found that if I used
a short piece of the old telecom single core copper wire & wrapped it around the
heater wire, doubled it up, then soldered them together, a good connection was made.
They don't take a lot of current so it worked fine.
NB: The centre rayon/nylon strands will just melt away when soldering.
Terminate in a 2 way terminal block or whatever takes your fancy.
You just have to experiment with the length of heater cable, but around 300 mm was good enough, when glued to the inside of the eye piece box underneath the eye pieces.
I ran mine directly off the 12 Volt supply & gave you about 3 or 4 Watts.
I'm posting this from memory, so the figures may be a tad.....out.
Can't remember the figures for the finder, but you can always try different lengths of heater wire until you get it right.
Place the heater on some gaffer tape & another layer of tape on top.
Makes a very flexible/durable heater.
Just remember that bench testing inside is not the same as out in the cold night air, so
you may have to bump the Wattage up a little.
eg; Shorten the heater wire or use parallel runs.
Have fun.
I forgot to mention that it's free, ie; if you have an old Electric Blanket hanging around.
(Maybe steal it from the "other side of the bed.")
Regs, L..
ps. Found an old thread on the subject.
My goodness, was I
that talkative?
>
http://www.iceinspace.com.au/forum/s...ght=dew+heater